Hibernate框架查询方式之QBC查询

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QBC(Query By Criteria)检索方式

简单查询，使用的是Criteria接口

List<Customer> list = session.createCriteria(Customer.class).list();
for(Customer customer : list){
 	System.out.println(customer);
}

排序查询

需要使用addOrder()的方法来设置参数，参数使用org.hibernate.criterion.Order对象

Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
Criteria criteria = session.createCriteria(Linkman.class);
//设置排序
criteria.addOrder(Order.desc("lkm_id"));
List<Linkman> list = criteria.list();
for(Linkman linkman :list){
	System.out.println(linkman);
}
tr.commit();

条件查询（Criteria是查询条件的接口，Restriction类是Hibernate框架提供的工具类，使用该工具类设置查询条件）
条件查询使用Criteria接口的add方法，用来传入条件。
使用Restrictions的添加条件的方法，来添加条件，例如：

• Restrictions.eq-----相等
• Restrictions.gt-----大于号
• Restrictions.ge-----大于等于
• Restrictions.lt----小于
• Restrictions.le----小于等于
• Restrictions.between-----在…之间
• Restrictions.like----模糊查询
• Restrictions.in----范围
• Restrictions.and----并且
• Restrictions.or====或者

Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
Criteria criteria = session.createCriteria(Linkman.class);
//设置排序
criteria.addOrder(Order.desc("lkm_id"));
//设置查询条件
criteria.add(Restrictions.or(Restrictions.eq("lkm_gender","男"),Restrictions.gt("lkm_id",3L)));

   @Test
    public void run1(){
        Session session =HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria critera  = session.createCriteria(Customer.class);
        List<Customer> list= critera.list();

        for(Customer customer : list){
            System.out.println(customer);
        }
        tr.commit();

    }


    //排序查询
    @Test
    public void run2(){
        Session session =HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria criteria = session.createCriteria(Linkman.class);

        //调用排序的方法
        criteria.addOrder(Order.desc("lkm_id"));
        List<Linkman> list = criteria.list();
        for(Linkman linkman : list){
            System.out.println(linkman);
        }

        tr.commit();

    }

    //分页查询
    @Test
    public void run3(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria criteria = session.createCriteria(Linkman.class);
        //设置分页的方法
        criteria.setFirstResult(0);
        criteria.setMaxResults(3);

        List<Linkman> list = criteria.list();
        for(Linkman linkman :list){
            System.out.println(linkman);
        }
        tr.commit();

    }


    //条件查询
    @Test
    public void run4(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria criteria = session.createCriteria(Linkman.class);

        //使用方法添加条件,两个条件默认是and连接
      //  criteria.add(Restrictions.eq("lkm_gender","男"));
     //   criteria.add(Restrictions.gt("lkm_id",3L));

//between
      //  criteria.add(Restrictions.between("lkm_id",2L,5L));

        //in方法查询
        //SQL :select * from cst_linkman where lkm_id in (1,2,7);
        List<Long> params = new ArrayList<Long>();
        params.add(1L);
        params.add(2L);
        params.add(7L);

        criteria.add(Restrictions.in("lkm_id",params));
        List<Linkman> list = criteria.list();
        for(Linkman linkman : list){
            System.out.println(linkman);
        }
        tr.commit();
    }

    @Test
    public void run5(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria criteria = session.createCriteria(Linkman.class);

        //SQL:select * from cst_linkman where lkm_gender = ? or lkm_id > ?
        //SQL:select * from cst_linkman where lkm_gender = '女' or lkm_id > 3L

        criteria.add(Restrictions.or(Restrictions.eq("lkm_gender","女"),Restrictions.gt("lkm_id",3L)));
        List<Linkman> list = criteria.list();
        for(Linkman linkman : list){
            System.out.println(linkman);
        }
        tr.commit();
    }


    //判断值是否为空
    @Test
    public void run6(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();

        //创建QBC查询接口
        Criteria criteria = session.createCriteria(Linkman.class);

        //查找所以的email为空的值
        criteria.add(Restrictions.isNull("lkm_email"));

        List<Linkman> list = criteria.list();
        for(Linkman linkman : list){
            System.out.println(linkman);
        }
        tr.commit();

    } 

聚合函数查询

Projection的聚合函数的接口，而Projections是Hibernate提供的工具类，使用该工具类设置聚合函数查询

• 使用QBC的聚合函数查询，需要使用criteria.setProjection()方法

Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
Criteria criteria = session.createCriteria(Linkman.class);
criteria.setProjection(Projections.rowCount());
List<Number> list = criteria.list();
Long count = list.get(0).longValue();
system.out.println(count);
tr.commit();

    public void run8(){
    Session session = HibernateUtils.getCurrentSession();
    Transaction tr = session.beginTransaction();

    //创建QBC查询接口
    Criteria criteria = session.createCriteria(Linkman.class);

    //设置聚合函数的方式
    List<Number> list = criteria.setProjection(Projections.count("lkm_id")).list();

    Long count = list.get(0).longValue();
    System.out.println(count);


    //再设置一遍setProjection方法
    criteria.setProjection(null);

    //继续查询所有的联系人 select * from 表、
    List<Linkman> mans = criteria.list();
    for(Linkman linkman : mans){
        System.out.println(linkman);
    }
    tr.commit();

   } 

离线条件查询

 @Test
    public void run10(){
        Session session = HibernateUtils.getCurrentSession();
       Transaction tr = session.beginTransaction();

       //创建离线条件查询的对象
       DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Linkman.class);
       //添加查询的条件
       DetachedCriteria add = detachedCriteria.add(Restrictions.eq("lkm_gender", "女"));
        //查询
       List<Linkman> list = add.getExecutableCriteria(session).list();

       for(Linkman linkman : list){
           System.out.println(linkman);
       }
       tr.commit();
   } 

SQL的查询方式

      Session session = HibernateUtils.getCurrentSession();
       Transaction tr = session.beginTransaction(); 

SQLQuery sqlQuery = session.createSQLQuery("select * from cst_linkman where lkm_gender=?");
sqlQuery.setParameter(0,"男");
sqlQuery.addEntity(Linkman.class);
List<Linkman> list = sqlQuery.list();
System.out.println(list);
tr.commit();

  @Test
    public void run11(){
       Session session = HibernateUtils.getCurrentSession();
       Transaction tr = session.beginTransaction();
       SQLQuery query = session.createSQLQuery("select * from cst_linkman");
       List<Object[]> list = query.list();
       for(Object[] objects: list){
           System.out.println(objects);
       }
       tr.commit();


   }

    @Test
    public void run12(){
        Session session = HibernateUtils.getCurrentSession();
        Transaction tr = session.beginTransaction();
        SQLQuery query = session.createSQLQuery("select * from cst_linkman");
       
        query.addEntity(Linkman.class);
        List<Linkman> list = query.list();
        for(Linkman linkman : list){
            System.out.println(linkman);
        }
        tr.commit();


    }